A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p – n junction diode that emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons.

The first visible-light led’s were also of low intensity and limited to red. Modern led’s are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

Recent developments have produced led suitable for environmental and task lighting. Led’s have led to new displays and sensors, while their high switching rates are useful in advanced communications technology.

LEDs have many advantages over incandescent light sources, including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching.